Assessing the age of relief growth in the Andes of northern Chile: Magneto-polarity chronologies from Neogene continental sections

The Andes of northern Chile currently experience a phase of relief rejuvenation as indicated by valleys that are >1000 m dissected into pediplains. However, it has been unclear when this phase of relief enhancement started. This paper discusses the use of palaeomagnetic chronologies from four sections in the Taracapá-Region (northern Chile) to assess this age. The sections are located in distal and proximal positions. Sediment accumulation occurred between c. 22.5 and 8/ 7.5 Ma with a hiatus that possibly spans a time interval between c. 19.5 and 11 Ma. The magnetic polarity chronologies suggest a preferred age between 8.0 and 7.5 Ma for the time when relief growth started. In proximal positions, however, alternative correlations suggest an age of 8.5 Ma. In addition, the palaeomagnetic data reveal no rotation of the analysed strata, suggesting a minimum age of c. 22.5 Ma for the tectonic block rotation south of the Arica deflection. © 2005 Blackwell Publishing Ltd.